Trimodally porous N-doped carbon frameworks with an interconnected pore structure as selenium immobilizers for high-performance Li-Se batteries

Abstract

Modulating the pore structure of cathode hosts is necessary to achieve high-performance Li-Se batteries with long-term cycling stability and superior rate capability. In this study, we demonstrate a novel strategy for the fabrication of trimodally porous N-doped carbon frameworks with an interconnected network as efficient cathode hosts for Li-Se batteries. This strategy utilizes the carbonization of SiO2/polyvinylpyrrolidone/Zn-based metal-organic framework mixtures and subsequent chemical etching of SiO2. During the carbonization process, the strong interaction between polyvinylpyrrolidone and metal-organic framework polyhedrons modulates the pore structures of the carbon hosts, leading to the formation of mesoporous carbon cages with microporous shell in the structures, rather than microporous polyhedra. In addition, SiO2 etching forms a macroporous “inverse opal” structure. This unique trimodal pore structure provides ample space for loading Se into the small-size pores and facilitates penetration of the electrolyte deep inside the cathode through the large-size pores. Thus, the Se-containing trimodally porous N-doped carbon frameworks deliver high discharge capacities (529 and 463 mA h g−1 at the 2nd and 300th cycle, respectively, at 0.5C) and exhibit excellent rate capability (235 mA h g−1 at 10.0C).